Previously, hydroxy-terminated polybutadiene (HTPB) compositions employing HTPB binders, plasticizers, wetting agents, and high solids loadings were crosslinked with trimethylol propane (TMP) along with isophorone diisocyanate as the isocyanate curing agent which functioned as the crosslinking and chain extension agent. The TMP and other similar compounds have functioned quite well in their field of use; however, the TMP is a solid melting at about 150.degree. F. Therefore the compositions must be mixed or processed at about this or a higher temperature to ensure that the TMP is dissolved.
Desirable would be a crosslinking, curing, and chain extension agent that is not a solid at ambient temperature which would permit composition processing at ambient temperatures.
Therefore, an object of this invention is to provide a variety of multi-functional isocyanates which can serve as curing agents to achieve composition binder chain extension and crosslinking functions.
Another object of this invention is to provide a variety of multi-functional isocyanates which can be used as a mixture in varying the amounts of the di- or tri-functional isocyanates to cure a HTBP polymer composition to obtain a wide range of mechanical properties.